Larson Davis 831C-FFT, Reference Manual, Page: 170 / 254

SoundAdvisor Model 831C A-6
Windspeed Pulse Input : Input accepts 0 to +3 pulses
from anemometer (+5V tolerant), 100k
Ω
load, setting
selects function
Analog Inputs : 3 channels, 0 to +2.5 V, 100k
Ω
load,
settings for scale and offset
A.1.12 I/O Connector Pinouts Specifications
The pinouts for the I/O Connector are shown in Table
A.4 .
Table A.4
1. To enable the “Logic In, Logic Control Input” fea-
ture, when making your own cable, pin 12 (Mains
Power Status) must be driven by a resistance
lower than about 20k

. This may be done by con-
necting a 10k

resistor from pin 12 to either pin
13 (+2.5V, to simulate running on Mains power) or
to pin 1 or 5 (Ground, to indicate running on
external battery power). Pin 4 needs to be driven
high to assert the Logic In and pulled low to de-
assert the input. It should not be left floating.
This can be done with a momentary push-button
switch from pin 4 to pin 13 with a 10k

pull down
resistor to ground (10k

from pin 4 to pin 1 or 5).
A.1.13 Battery Specifications
Size : 4 x AA size cells (LR6)
Types : 1.5 V Alkaline, 1.2 V NiMH rechargeable, 1.5 V Photo–Lithium
NiMH Charge Time : USB to power outlet (not PC), meter powered OFF during
charging < 16 hours
Typical Operating Time : > 8 hours continuous measurement
Pin # Description Signal Type
1 Ground, Digital and Power
Supply
Ground
2 Logic Out 1, Logic Control
Output
Output, 0 to +2.7
V
3 831 Activity Output, 0 to +2.7
V
4 Logic In, Logic Control
Input
Input, 0 to +5 V
5 Ground, Digital and Power
Supply
Ground
6, 7 Vext, External Power Input Input, +10.8 to
+30 V, 0.5 A
auto-resetting
PTC fuse
8 SensorClk_L, LD 426A12
digital sensor clock
Output, open
drain, +20 V max.
open and 50 mA
max. closed
9 SensorDIO, LD 426A12
digital sensor data
Bi-directional,
+2.7 to +5 V logic,
open drain
10 CalOn_H, LD 426A12
calibration signal on
Output, 0 to +2.7
V
11 Ovld, LD 426A12 overload
detection signal
Input, 0 to +5 V
12 Mains Power Status; OK
when +2.7 V
Input, 0 to +2.7 V
13 +2.7 V to supply logic
switches
Output, +2.7 V
through 220

14 Wind Speed In, Pulse
input for wind speed
sensors
Input, +5 Vpp
max.
15 Vwthr1, Analog to Digital
Converter Input, Wind
Direction
Input, 0 to +2.048
V, 100k  load,
scale with series
resistor
16 Vwthr2, Analog to Digital
Converter Input,
Temperature
17 Vwthr3, Analog to Digital
Converter Input, Humidity
18 Analog Ground, Signal
ground for pins 15
through 17
Ground
Pin # Description Signal Type